Purpose of DPF Regeneration

　　1. Increase exhaust temperature to decompose soot in the DPF. Reduce hydrocarbons in the DOC.

2. Remove sulfur deposits on the SCR catalyst and clear crystals formed on the DEF nozzle.

　　3. Raise the temperature sufficiently to carry out regeneration.

　　With the advent of Selective Catalytic Reduction (SCR), the combustion process inside the engine has changed. Due to advanced fuel timing, nitrogen oxides increase during engine shutdown while soot decreases, greatly extending the time for soot generation in the regeneration system. Additionally, the increased nitrogen oxides in the exhaust help oxidize soot at lower temperatures.

　　Regeneration Trigger Methods

　　Soot: The DPF collects soot produced by the engine. Automatic regeneration is performed periodically to reduce soot.

　　Start-up Regeneration: After a cold engine start, the engine control module initiates start-up regeneration. This regeneration is performed to heat the system to the required temperature to begin adding DEF.

　　SCR Maintenance: Regeneration is performed to maintain the SCR system. This regeneration is triggered when ammonia slip or poor nitrogen oxide conversion occurs.

　　ARD Maintenance: Regeneration is performed to maintain the ARD system. Fresh fuel must flow through the ARD head to heat the recirculation nozzle. The heated recirculation nozzle is used to clean the ARD nozzle.

　　Regeneration Implementation - Clean Emissions (CEM)

　　 Perkins The Clean Emissions (CEM) in the engine includes the following components:

　　Aftertreatment Regeneration Device (ARD)

　　Diesel Oxidation Catalyst (DOC)

　　Diesel Particulate Filter (DPF)

　　Selective Catalytic Reduction (SCR) System

　　Carbon monoxide and hydrocarbon (HC) exhaust emissions from the engine enter the CEM and first pass through the Diesel Oxidation Catalyst (DOC). The DOC is located at the inlet of the Diesel Particulate Filter. The main purpose of the DOC is to oxidize unburned hydrocarbons, carbon monoxide, and soluble organic fractions in the exhaust into carbon dioxide and water. The DOC also acts on nitrogen oxides, increasing the content of nitrogen dioxide to improve the efficiency of the Selective Catalytic Reduction system.

　　Next, the exhaust enters the Diesel Particulate Filter (DPF), which is a particulate trap capable of reducing particulate emissions by up to 90%. The filter has a honeycomb structure with channels that are open at one end and blocked at the opposite end. Exhaust enters the open end, passes through the porous channel walls, and exits through adjacent channels. Soot particles too large to pass through the pores accumulate on the channel walls. The solid particles collected by the DPF consist of soot (carbon) produced by incomplete fuel combustion, which can be removed from the DPF by regeneration. Ash is also collected by the DPF. Ash is the non-combustible residue left from burning oil and must be removed using special maintenance procedures.

　　Then the exhaust enters the Selective Catalytic Reduction (SCR) mixing chamber, where Diesel Exhaust Fluid (DEF) is injected into the gas. The exhaust and DEF mix in the chamber and then enter the Selective Catalytic Reduction canister (1). The mixture breaks down into ammonia and carbon dioxide and enters the reaction chamber (2). The SCR reaction chamber is a cordierite catalytic substrate coated with a copper zeolite washcoat inside the SCR canister. The outlet section has another coating, making it a Selective Ammonia Oxidation (AMOX) catalyst (3). Once the temperature is high enough, the water in the DEF evaporates, and the urea in the DEF converts to ammonia. Once converted, the ammonia is absorbed by the catalyst. As the exhaust passes through the catalyst, nitrogen oxides in the exhaust react with ammonia and the catalyst, converting the gases into nitrogen and water vapor, meeting increasingly stringent emission standards and protecting the blue sky and white clouds for everyone!